1. Field of the Invention
The present invention relates to a starter for starting an internal combustion engine, and relates in particular to a freely ejecting starter.
2. Description of Related Art
Frequently, so-called Bendix-type starters are used as electric starters for starting an internal combustion engine. These starters have an electric starter motor, the drive shaft of which drives a pinion shaft that is shiftable in a housing of the starter in the axial direction and that bears a pinion outside of the housing. The drive shaft has an external toothing in the form of a coarse thread, which mates with a complementary internal toothing of a clutch element, shiftable together with the pinion shaft, of a roller-type overrunning clutch between the drive shaft and the pinion shaft. Following the start of the internal combustion engine, the roller-type overrunning clutch prevents the starter motor from being driven by the internal combustion engine at an excessively high speed and thus damaged. To start the internal combustion engine, the starter is switched on, whereupon the pinion is meshed into a gear wheel or a ring gear of the internal combustion engine in that an meshing mechanism of the starter shifts the pinion shaft together with the clutch element of the overrunning clutch from an off position or rest position of the pinion into an meshing position, in which the pinion is meshed into the gear wheel or ring gear of the internal combustion engine and mates with it. When the pinion is driven by the starter motor in the meshing position via the drive shaft, the overrunning clutch and the pinion shaft in order to rotate the gear wheel or ring gear of the internal combustion engine, great reaction forces act on the pinion shaft in the region of the pinion.
While in so-called jaw starters the pinion shaft is supported on both sides of the pinion and may hardly be deflected by the radial forces acting on the pinion, in so-called freely ejecting starters the pinion shaft is supported only on one side of the pinion, namely within the housing of the starter. In a deflection of the pinion shaft as a result of the radial forces applied on the pinion, the pinion shaft in this case is suitably supported on the drive shaft via a bushing situated between the drive shaft and the hollow pinion shaft. Depending on the tolerance situation of the plays in the bearing and in the bushing, however, usually a part of the forces is also introduced via the rollers of the overrunning clutch into the clutch element and from there via the engaged toothings of the clutch element and of the drive shaft into the latter. As a result, there is a very high load applied locally on the opposite roller tracks developed on the pinion shaft and on the clutch element, which may result in an early wear of the roller tracks and thus in a reduction of the service life of the overrunning clutch and of the starter.